1. Field of the Invention
This invention relates in general to an apparatus and method for detecting leaks from underground tanks containing hydrocarbon liquids, and in particular to a method using a dye which is soluble in hydrocarbon.
2. Description of the Prior Art
Service stations store gasoline in underground tanks. These large tanks may be made of fiberglass or steel covered with fiberglass. Precautions are taken to minimize the chance of leakage of gasoline from the tank.
Nevertheless, leakage does occur, particularly from the older tanks. Undetected leakage can enter the ground waters in the earth, contaminating the water. The hydrocarbon leakage can run off into drainage pipes and result in the gasoline entering fresh water supplies. Also, the gasoline vapors can create fire hazards in storm and sewer drains.
A leaking underground gasoline tank is difficult to detect. Unless the vapor can be smelled or liquid detected in manholes for storm or sewer drains, one would not know that the tanks are leaking. Also, even if gasoline is discovered in a storm drain or sewer pipe, it may be difficult to determine from which tank the leak is occurring. Often, there will be a number of tanks and service stations located near each other.
One system that has been used recently utilizes a dye that is soluble in hydrocarbons, but not in water. When installing the tanks, the dye is placed in the fill material around the excavation. As a result, if the dye comes into contact with leaking gasoline, it will cause the gasoline to change colors. If the colored liquid shows up in a manhole or other area a distance away from a number of tanks, the color will indicate from which service station the leak is occurring. Each adjacent service station would use a dye material of a different color.
While such a system works, it still does not inform one of leakage unless the leakage is observed in a sewer or storm drain manhole or at some other area. Also, it requires a new installation of tanks. A number of patents exist showing other methods for detecting leaks from gasoline storage tanks.